Continuous-Time Symbol Detector for IR-UWB Rake Receiver in 90 nm CMOS

In this paper, a coherent continuous-time symbol detector suitable for a simple RAKE receiver using single-bit correlation is reported. A working chip with fully integrated digital symbol detection without any clocks, ADC and filters for simple and power efficient CMOS implementation has been presented. Cross-correlating RAKE receiver with on-off keying is the most challenging receiver due to its hardware implementation complexity. Also process variations in 90 nm CMOS technology impose significant design challenges to the delayline. Optimal design of the delay elements and the use of pulse width controller blocks (PWC) along the delayline allows narrow pulses through the system significantly reducing the process variation impact. The optimized delayline combined with the high-speed counter and the match thresholder constitute a complete continuous-time IR-UWB RAKE receiver. With a data rate of 1.5 Mbit/s and a power consumption of 2.36 mW, operation of the symbol detector in continuous-time is verified with measured results. The symbol detector along with the ranging system in a master-slave configuration can estimate time-of-flight (ToF) value which aids localization.